Study: Marijuana Use Not Associated With Previously Reported Changes In Brain Morphology

Study: Marijuana Use Not Associated With Previously Reported Changes In Brain MorphologyIt was less than a year ago when the mainstream media was chock-full of headlines like this one: ‘Brain changes associated with casual marijuana use in young adults, study finds.’ The alarmist headlines were in response to a controversial paper published by researchers at Harvard University in Boston and Northwestern University in Chicago which alleged to have found differences in brain morphology in a cohort of 20 college-age marijuana users as compared to 20 non-users. The study’s investigators attributed the differences to subjects’ cannabis use.

But a funny thing happened when a team of scientists from the University of Colorado and the University of Kentucky tried to replicate these results in a separate, larger sample (158 participants) of subjects after rigorously controlling for both groups’ use of alcohol.

They couldn’t.

Writing in the January 28 edition of The Journal of Neuroscience, authors summarized:

“[T]his retrospective study examined brain morphology in a sample of adult daily marijuana users (n = 29) versus nonusers (n = 29) and a sample of adolescent daily users (n = 50) versus nonusers (n = 50). Groups were matched on a critical confounding variable, alcohol use, to a far greater degree than in previously published studies.

We acquired high-resolution MRI scans, and investigated group differences in gray matter using voxel-based morphometry, surface-based morphometry, and shape analysis in structures suggested to be associated with marijuana use, as follows: the nucleus accumbens, amygdala, hippocampus, and cerebellum.

No statistically significant differences were found between daily users and nonusers on volume or shape in the regions of interest. Effect sizes suggest that the failure to find differences was not due to a lack of statistical power, but rather was due to the lack of even a modest effect.”

Why the contradictory results? Investigators speculated that previously reported imaging studies failed to adequately control for the impact of alcohol, a substance that “unlike marijuana, … has been unequivocally associated with deleterious effects on brain morphology and cognition in both adults and adolescents.” In other words, researchers theorized that previously reported differences in the brain images of marijuana consumers as compared to non-users were likely because of subjects consumption of booze, not cannabis.

They concluded, “In sum, the results indicate that, when carefully controlling for alcohol use, gender, age, and other variables, there is no association between marijuana use and standard volumetric or shape measurements of subcortical structures. … [I]t seems unlikely that marijuana use has the same level of long-term deleterious effects on brain morphology as other drugs like alcohol. The press may not cite studies that do not find sensational effects, but these studies are still extremely important.”

An abstract of the study, “Daily Marijuana Use Is Not Associated with Brain Morphometric Measures in Adolescents or Adults,” is online here.

34 thoughts

  1. that and there’s evidence that it protects against Alzheimer’s,and now the evidence is out that it has protective properties against a whole host of inflammatory-process diseases like cancer, diabetes, arthritis. In fact, it’s starting to look like we all should be smoking a little hooch.

    it’ll be interesting to see 10 years down the road if there is an inverse correlation between regular cannabis consumption and these inflammatory diseases.

  2. “To say that cannabis is in no way related to alcohol is a led zeppelin at NORML.”

    Do you folks see how insidious propaganda can be? Even NORML has mentally blended marijuana and alcohol together. Even though they know it is not, the mental association is too strong between partying and drinking and smoking marijuana is too strong for people to make good sense of what they see; apparently. I don’t really know what to make of these kinds of mental tricks we play on ourselves.

    NORML, that shouldn’t be a lead zeppelin; it should be obvious!

    The bad effects of alcohol and tobacco keep being dumped at marijuana’s feet and it is beyond stupid.

    [Editor’s note: Alcohol and cannabis are self-evidently not the same. But, both drugs cause impairment, therefore standards of impairment and accurate testing for such re cannabis is not only coming, but has been invited by NORML (and all of the other drug policy reform groups) for decades.]

  3. Ha! Haaaa! Universities in pro cannabis states are being funded for authentic scientific studies! And with time to spare! Judge Mueller still has not made her decision. If studies keep pouring out at this rate, take your TIME Judge! We can wait a few more weeks for your decision!

  4. Irreproducible results! Yet prohibitionists like Dr. Andrew Harris will cite the changes-in-brain-morphology study for decades to come.

    HINT: If your physician is treating you based on irreproducible, 30-year-old studies, find a new physician.

  5. A question I have pertaining the study mentioned:
    They used a control group which did not use Cannabis for the last 60 days. People from that group could therefore have used it in the past. (see section Materials and Methods for details) If Cannabis was associated with irreversible brain alterations it could be that no changes were found because the control group already had irreversibly altered brain structure..Why did they not use a control group which had not used Cannabis at all?

    Sincerely
    M. Schärer

  6. These Journal of Neuroscience level scientists assume that the brain is a story telling data processor that can be hurt by marijuana. Would your mind fit in a small mechanical box? No, so don’t claim you can MRI a thought or idea in high resolution and then tell us weed “has been unequivocally associated with deleterious effects on brain morphology and cognition in both adults and adolescents”.

    [Paul Armentano responds: “so don’t claim you can MRI a thought or idea in high resolution and then tell us weed “has been unequivocally associated with deleterious effects on brain morphology and cognition in both adults and adolescents”. The study’s authors said just the opposite.]

  7. I am a firm believer in puff puff pass and this study does appear to be much more scientific BUT….regardless of any studies think that use of any substance by teens in their developmental years is a bad idea….19 maybe 20 or so do as you please but moderation is always a good idea

  8. It occurs to me that the research revenue has increased greatly in pro-cannabis states such as those mentioned in this study from the Universities of Kentucky and Colorado. Hemp Hats off to the brave students and faculty involved in this vital research.
    The money trails from prohibition have deep roots, but they’re not as strong as they used to be. I just heard an NPR report about wealthy investors using Canada’s banking system to get loans to create enormous indoor grow operations just north of Washington state. Just think, Congress; All that money going to Canada, preventing violence with herbal medicine, because we’d rather spend more on law enforcement ? All those lights and electricity to power a small village when we could be growing hemp right under the Kentucky sun and creating jobs without spending a dime… And this is the Congress that’s all about “cutting spending?” How about cutting subsidies from pharmacuetical companies taking jobs out of the country to sell us poison when we could be subsidizing medicinal marijuana with the revenue from growing industrial hemp and recreational marijuana… and creating sustainable career JOBS right here in the U.S. Of A?!
    …oh wait; must be that encaphalitis again… That’s alright, I’ve gotta cure for that…

  9. The Brain Mythology Scare Studies weren’t reported to have considered vital differences in use practice, as whether H-ot B-urning O-verdose M-onoxide Joints were used as apposed to Vaping 25-mg single tokes.

    l. Whether carbon monoxide ALONE could be causing behavior or morphochanges attributed to cannabis, or

    2. the SYNERGY based on a carbon monoxide drug cocktail being invariably present whenever a particular user used cannabis?

    The study reported by Armentano above (158 individuals) may or may not put this issue to rest. TFMR Time for more research to see if ELIMINATING COMBUSTION will once and for all eliminate ‘marijuana” drug effects.

    PS1. not cannabis,
    the Joint is the Gateway Drug–
    to nicotine $igarettes!

    PS2. Yes you can Vape (195C/385F)
    with a flexdrawtube one-hitter–
    suck slow,
    don’t glow
    till after 19
    seconds or so.

    PS3. Double-ended breathbonnet
    for you and for me!

  10. @David – In spite of being too high to think straight, you did a real good job spelling and using proper grammar! I’ll bet you couldn’t do that if you drank a 5th of whiskey, or if you took heroin, or meth, or many other legal drugs….

  11. @M Sharer

    “They used a control group which did not use Cannabis for the last 60 days.”

    I don’t see this in the abstract. Where did you see this?

  12. @M. Scharer

    It appears to me that the changes in brain morphology were never inferred to be permanent. It seems highly unlikely to me that the researchers would make such a major, glaring mistake. After all, these are not cruel, drug war zealots, such as William Bennett and Dr. Andy Harris. These are scientists interested in the truth. (They seem to think the truth will set us free for some reason. They may be right. I remember polio scares from the 1950s. Science set me (and all us) free from that worry.)

    When I stop vaping for a few weeks, I slowly begin to play and write less music. Instead I study music theory as applied to the guitar fret board. I have no idea why this is, but it is interesting given the results of the study.

  13. Changes in brain morphology occur naturally as we age, expose our bodies to pollutants, preservatives, and abusive intolerance. Cannabis helps guide us through the change.

  14. @Galileo Galilei
    As they found no association between marijuana use and standard volumetric or shape measurements of subcortical structures in daily users I don’t understand what you mean by “never inferred to be permanent”? Obviously if no differences in subcortical brain structures were found it makes no sense to talk about (ir)reversibility of brain structures, because in this study they appear to be similar in daily users and controls..
    However if they used a control group which did not use Cannabis for 60d (90d for adolescents) and which consisted (on behalf of the adolescent part) of people engaged in risky behaviours it would at least be possible that some of the controls (either adults or adolescents) used Cannabis prior to the abstinence period (which is 60d for adults and 90d for adolescents). Therefore IF Cannabis use leads to brain alterations which take more than 60 (90) days to recover, it would be possible that no differences between users and controls were found because the brain of controls did not recover during the 60 (90) days. To put this into context, some (functional) brain alterations of alcohol abuse take months to multiple years to recover from, so it is not unlikely that another intoxicant like Cannabis could produce brain alterations which take at least multiple months to fully recover from.
    In the study they do not mention if people from the control group used Cannabis prior to the 60 (90) days which they even admit in the discussion part of the study:

    “Other limitations of our study include group designation based on recent marijuana use rather than detailed history (e.g.,
    age of onset, duration of both marijuana and alcohol use) as well as no inclusion of socioeconomic factors (e.g., maternal drug use, early life stress, nutrition), which may impact brain morphology during development. A number of systematic differences in these factors may have contributed to the group differences found in
    previous studies (Filbey et al., 2014; Gilman et al., 2014) or masked an effect in this study”

    I even wrote an email to Rachel Thayer which co-authored the study and asked why they did not use a control group which did not use MJ at all, so far I did not receive an answer.

  15. Your initial comments mentioned “irreversible brain alterations” which suggested to me you assumed the changes were permanent when obviously the study assumed the opposite. You seem to have a great deal of familiarity with the methodology used in this type of study. I’m a lay person unfamiliar with the studies of the brain, so I assumed there was some reason for the 60 day interval. It takes about a month of abstinence for my mind to move from artistic to analytical, so the 60 day interval seems plausible to me.

    It took decades, but I finally realized I couldn’t believe anything coming from the government involving marijuana, so I have to go by my own experience. My IQ measures exactly the same as it did in kindergarten, so no measurable brain dysfunction has occurred. I once read that marijuana causes sexual dysfunction. Fortunately my dangling little friend never found out about that study. Indeed, marijuana is the only true aphrodisiac I’ve ever encountered in my life. I have little libido without it. Yet the government tells me marijuana causes sexual dysfunction. I’ve stopped believing the government.

    If the proper way to perform a study of this nature is the approach you suggest, then why is any study ever done differently? Maybe funds? Now that the greatest generation, who fell victim to the government’s anti-marijuana propaganda, are dying off, maybe the authors didn’t have the time and funds to canvas the community sufficiently to find someone who hasn’t toked in 60(90) days. Sixty(90) days is a long time, man.

    Incidentally, it seems to me toking is among the least risky behaviors you can engage in. Just driving to the store is more risky. Driving back from your favorite watering hole is even more risky to you and everyone on the road.

  16. @Galileo Galilei
    I agree with you that many studies are flawed. This is why I eagerly discuss the methodology used in studies. Most studies on MJ are flawed in one or the other way. Mostly it’s a matter of convenience, meaning they could not find people who engage in risky behaviours but did never use MJ (like this study) or they used people who used other drugs too (like alcohol. cocaine, XTC etc). As people with less risk aversion have different size for certain brain areas (e.g. orbito-frontal cortex) this could motivate the approach to use people who might have used Cannabis in the past but did not for 60 (90) days because it would make users and controls similar in terms of risk taking. This could be a motivation for this study methodology. However theoretically it would be possible to do a proper study with people which also have less risk aversion but do not do drugs (people who compulsively gamble for example). Obviously such as control group would be more difficult to find but could answer the question unequivocally.
    Often researchers are pushed to publish a certain amount of papers a year which ultimately makes no sense as we could do endless studies with erroneous methodology yielding no clear conclusion(s). Opposed to we could invest in one properly designed study which could answer the question thoroughly.

    I would however not agree that experience can give you certainty as does proper study design. There is a reason why in epistemology double blind study design is used. It’s because you can’t trust anyone, not even yourself (especially when it comes to drugs).

    Some further reading about orbito-frontal cortex volumina and risk taking
    http://www.pnas.org/content/109/2/425.short

    Some further reading how education might alter (initial) IQ scores.
    http://psycnet.apa.org/journals/pag/28/2/515/
    http://www.mitpressjournals.org/doi/abs/10.1162/jocn_a_00445

    Cheers!

  17. “Obviously such as control group would be more difficult to find but could answer the question unequivocally. Often researchers are pushed to publish a certain amount of papers a year which ultimately makes no sense as we could do endless studies with erroneous methodology yielding no clear conclusion(s). Opposed to we could invest in one properly designed study which could answer the question thoroughly.”

    The methodology could be better, but it isn’t as though there is any “smoking gun” in the first study regarding marijuana either! The researchers of the first study did state that the marijuana users did not appear to be suffering from any kind of mental issues, that they could not attach the brain changes to harms caused by marijuana. They stated exactly this in the first study that assholes keep citing as proof that marijuana damages the developing brain.

    And that folks, is a lie!

  18. Mike, the answer to your question is very simple. It seems like the designers of the study didn’t want to rely on self-reported data. People tend to lie on drug use questionnaires, no matter how anonymous they are. I assume they conducted drug screens on the control group which would give them an almost definitive answer for whether any of the subjects had used cannabis within the said timeframes. Due to the drug test limitations, they couldn’t know with certainty whether any of them used it before these timeframes; therefore, as to not corrupt the integrity of the study, they have mentioned such limitations. It does not mean that the entire control group were users beforehand;it’s just that they don’t know whether they ever were.

  19. @Leo

    If you read the study (I provided the link above in one of my previous posts) you will realize that they used the TLFB questionnaire.

    Quote from the study:

    “Participants completed the Time Line Follow Back (TLFB) to assess
    quantity and frequency of substance use for the past 60 d (Sobell and
    Sobell, 1992), the AUDIT to assess hazardous drinking/dependence
    (Saunders et al., 1993), the Impulsive Sensation-Seeking Scale (IMPSS)
    of the Zuckerman–Kuhlman Personality Questionnaire (Zuckerman et
    al., 1993), the Beck Depression Inventory (Beck et al., 1961), and the Beck
    Anxiety Inventory (Beck et al., 1988).”

    “Based on the TLFB data, a subset of subjects was identified as daily
    marijuana users (n ? 29, 16 male and 13 female). From the remaining
    subjects, age, gender, and AUDIT scores were used to create a matched
    control group reporting no marijuana use in the past 60 d.”

    What is TLFB:
    http://cde.drugabuse.gov/instrument/d89c8e23-16e5-625a-e040-bb89ad43465d

    cheers!
    Mike

  20. Mike, I didn’t say they abandoned the questionnaire all together. I just assumed that they used drug testing to back it up because the said timeframes would make sense if that was the case. I find this strange that they didn’t mention this in the study. Perhaps it was done without the participants’ knowledge, and therefore they don’t have a consent to publish this data. Ok, even if you say that the control group were past users who stopped more than 2 months ago, there’s absolutely no evidence that cannabis causes any kind of impairment past a one month mark; therefore, even if there were permanent changes in the brain’s morphology, this study clearly demonstrates that they are not functionally significant, and that’s good enough for me.

  21. Mike, they did identify the heavy marijuana users and compared their brain structures to the control group. This was exactly the point of the study… Why are you saying they should have used a non-marijuana using control group? The point of the study was to confirm or disprove the first study which says, “marijuana causes alterations to the brain in a dose dependent fashion”.

    Clearly, they were supposed to include some moderate marijuana users in their control or the results wouldn’t be valid, yet you argue the opposite… Huh?

  22. @Leo

    “Perhaps it was done without the participants’ knowledge, and therefore they don’t have a consent to publish this data.”

    => Another explanation would be that they just did not assess consumption pattern by measuring urinary traces and that they indeed only measured it via questionnaire as is mentioned in the study. As they gained consent for the study from the participants for all the other measurements I don’t see the point why they should not have asked for urinary samples which could have validated the consumption patterns indicated by the questionnaire.

    Obviously IF Cannabis caused irreversible brain alterations you could not use a control group who probably used Cannabis in the past to validate the claim that Cannabis caused no long-term brain changes. What is need would be a control group which did never use Cannabis and is similarly ranked in terms of risk taking (see my previous posts for further elaboration).

    Furthermore this study investigated subcortical brain structure volumina and shape. They did not test for functionally significance, they did not test for verbal fluency, abstract reasoning, working memory or reaction time. This is a study ONLY about the volumina and shape of brain regions.

    @Dave Evans
    Because in order to validate the claim the title of the study gives rise to, i.e. “Daily Marijuana Use Is Not Associated with Brain
    Morphometric Measures in Adolescents or Adults” you would need a control group who never used MJ. Otherwise, assumed Cannabis consumption caused irreversible brain alteration, controls would have these alterations and could therefore not be distinguished from daily users.

    As long as there exists no study which clearly demonstrates that the subcortical brain structures of people who used Cannabis but stopped some time ago are not different from people who never used Cannabis we cannot use people who used Cannabis but stopped as a control group. If you know a study which proves that please provide a link

    Can you please elaborate why they were supposed to use some moderate MJ users in the control group in order to make their study valid?

  23. Mike, you’re being a purest for no reason. OCPD much? The first study claims they have data demonstrating that marijuana causes brain damage and that the more marijuana you use the more damage they can see in their data.

    This study addresses the first one and debunks it main claim: Heavy marijuana users have more brain damage than moderate marijuana and they have more damage than light marijuana users who have more brain damage than non-users.

    Their control contained non-users, light users, and moderate users. They could not find damage in the heavy using group based that wasn’t related to their alcohol consumption. The first study said they should see a clear difference between the test group and the control. Why would we need to remove any and all marijuana user from the control??? Your requirement that the control should be all non-users would not help with their trying to separate the effects of alcohol from the effects of marijuana. Too many people use both and that was the point. We keep blaming marijuana for problems caused by alcohol because people tend to use them together. Where does one find a control that contains heavy drinkers, but not ex-potheads?

  24. @Dave Evans
    The title of the study (“Daily Marijuana Use Is Not Associated with Brain Morphometric Measures in Adolescents or Adults”)suggest that there are no differences in subcortical brain structures btw. daily users and non users. This however can obviously only be proven using a design where you compare users to never users.
    As I mentioned earlier we need a control group which does not use drugs/alcohol or any other medication and whose individuals are ranked similar in terms of risk taking. (Because risk taking is associated with volumina of certain subcortical brain structures e.g. orbito-frontal cortex)
    This study can be used to support the hypothesis that there is no dose-dependent effect. However this finding is not new because most psychological studies who ran cognitive test on ex-MJ users found that recency of use (rather than total use) is the most important predictive variable.
    Obviously alcohol has detrimental effects on cognition, especially if used regularly. However just because alcohol is legal does not mean we should not opt for the optimal solution in determining effects of Cannabis consumption on the brain. We already have a lot of faked and biased literature when it comes to alcohol’s effect on health (supposed cardio-vascular benefits for example, publication biases through industry funding etc.). As I mentioned earlier studies with a stringent methodology would obviously be more expensive. However they would be able to answer the question posed unequivocally.

  25. “This study can be used to support the hypothesis that there is no dose-dependent effect. However this finding is not new because most psychological studies who ran cognitive test on ex-MJ users found that recency of use (rather than total use) is the most important predictive variable.”

    And yet, we have 100’s of liars going around the country trying to change legislation based on the idea more marijuana use means more brain damage. Even though there has only been one rebuttal study; these idiots seem to see connections to brain damage that isn’t there and I don’t believe they even understand any of your critiques regarding the methodology of this or any study.

  26. Probably true. I’m from Switzerland and we could even vote on the issue in 2008. Shortly before the voting some scaremongering studies about bullous disease were released. The legalization was rejected with 63.2%. As always in politics (or was it poly-tics?) is not about facts but money, power and emotions. I have a flicker of hope that if we adhere to the most stringent methodologies we might actually change what people believe about the harms and benefits of MJ. This is however rarely going to happen if an amateur like me can find methodological weakness of a study while skimming the text. Needless to say professional fraudsters (i.e. politicians) will use every loophole to influence the opinion of the public for their personal benefit. We can close those loopholes by adhering to stringent methodologies.

  27. Mike, if you look at the study being reproduced, you will see that they also didn’t use a completely non-smoking controls. Yet, they still found a significant difference. If the findings were correct, this study should have confirmed it. It didn’t, but found that the exact statistical difference is attributed to alcohol use. This clearly means that methodology in the paper being tested is flawed. At the very least this study refutes the previous one. And you know, burden of proof and such…

  28. Mike,
    I meant that the Harvard study controls were also occasional partakers in cannabis, but didn’t smoke for a year. I didn’t mean tobacco smokers. But your point is correct nonetheless.

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